Passed CA Emissions

[tomtom72]

Originally Posted by tf95ZR1

I know I'm bringing up an old thread, but now this (and more) is an issue for me. I didn't pass CA smog.
Same HC and CO values that passed for the last 5 years now don't pass. My NO was higher than before at 15mph but lower at 25mph(?).
So I'm researching all of this. My understanding is that HC and CO increase with poor/incomplete combustion,
while too hot a combustion increases NO. So there is a "window" of temperature and combustion that is ideal.
Won't wrapping and possibly overheating the CATS increase NO?

What to do, What to do... I know, move to another state.

are the cats the OEM ones? If yes then I would change the O2 sensors as older ones will react a bit slowly over the life span. If the cats are the s/s metal spun substrate then you would do well to have a heat coating on them. s/s cools too quickly, or I should say transfers heat too quickly and the spun metal substrate ones actually do not do as good a job of cleaning up tail pipe emissions.

The trick of Hib's with the EGR is a sweet one! I have a 90 so I would have never thought of that trick! Kudos Hib!!


Tom

[zr1don]

In response to the inquiry about NOX and temperature, its true higher "combustion" temps will increase NOX, but thermowrapping promotes higher exhaust system temps, including raising the temp in the cat. The increased cat temps increases the efficiency of the cat reducing NOX.

[Paul Workman]

Don n Mike...

All very interesting stuff. Copied and pasted, against the odd chance I end up in Colorado, or some such other. Thanks for the detailed post! I thought the "hybrid" chip tuning was an interesting approach too!

P.

[Hib Halverson]

Originally Posted by Paul Workman

Hib,

CAGS = noise abatement? Ya might wanna check your sources! (snip)

Actually, I decided to do that over the weekend. I hadn't talked to him in a while and he refreshed my memory.

Over the years, I've gotten the story confused. CAGS does, in fact, exist for CAFE and avoiding guzzler but it also enabled the ZR-1 to get though the pass-by noise these, which back then, was only in the State of California.

Fuel economy was the main reason. California Highway Patrol's Pass-by noise was a second benefit.

Sorry for the confusion. I rely on what I remember happening too much sometimes.

[Hib Halverson]

Originally Posted by zr1don

In response to the inquiry about NOX and temperature, its true higher "combustion" temps will increase NOX, but thermowrapping promotes higher exhaust system temps, including raising the temp in the cat. The increased cat temps increases the efficiency of the cat reducing NOX.

This is true...but only to a certain extent. You have to be careful with exhaust wrap. Do the pipes before and after the car but not the cat itself.

Cats can get so hot the substrate fails and then you're in worse shape that before.

What I do before testing is take a 5 mile run on the freeway in 4th or 5th gear then pull into the test station. If the test station is not near the freeway, I'll drive around the block a couple of times in first gear. Either way gets the cats hot.

[Z51JEFF]

Well,just got back from my friendly neighborhood smog nazi and my Haibeck chipded,other wise 100% stock 18,000 mile 1991 ZR-1 FAILED!On NOX I think its 702 with a 502 max.So whats my solution here guys?Drove the car for 20 miles right to the smog station.Stock chip,octane booster and what brand of gas Im not sure.How do I get this this thing to pass?

[mike100]

You need to post the entire test result, but my NOx was 700 when it had a gaping vacuum leak under the plenum.

went to 390-400 when it was fixed.

[Bill]

I have read that thermo wrap on the headers would cause the metal to become brittle over time. Is there any truth to this? I thought about wrapping mine for several reasons.

[Hib Halverson]

Originally Posted by Z51JEFF

Well,just got back from my friendly neighborhood smog nazi and my Haibeck chipded,other wise 100% stock 18,000 mile 1991 ZR-1 FAILED!On NOX I think its 702 with a 502 max.So whats my solution here guys?Drove the car for 20 miles right to the smog station.Stock chip,octane booster and what brand of gas Im not sure.How do I get this this thing to pass?

Wow...that's failed by a ton!

Unfortunately, if the engine is running right, 90-92 owners have few options as far as EGR because they don't have an EGR valve. Plus the State of California wants to force old cars off the roads and one way it does that is by lowering the emissions limits which has been done at least twice since 1995.

First, stop using octane booster. Few of them are effective and the ones that are (which use MMT as the active ingredient) can damage your cat converters.

Specifically, what brand of octane booster have you been using?

Secondly, I'd inspect the engine looking for anything that will increase combustion temperature which raises NOx emissions. Check the engine over and report back to the forum on your findings?

Lastly, can you post the full results of your test?

[mike100]

I think on the other forum you clarified that you were not running the stock chip and plan to revert before re-testing? that would be a biggie right there, although I was able to get mine to barely pass with a chip when I pre-tested for fun.